1. Field of the Invention
The invention relates to ultrasonic inspection systems, and is particularly directed to a remote inspector including a holding device for performing in-service inspection of atomic reactors and the like.
2. Description of the Prior Art
Ultrasonic in-service inspection systems have been developed in the recent past for fast breeder reactors and both pressurized and boiling-water reactors. The technical approach which has been followed features remotely controlled traveling instrument carriers (a remote inspector), and computerized collection and storage of inspection data in a manner providing real-time comparison against predetermined standards. Numerous types of equipment have been proposed, heretofore, for accomplishing such inspections. However, none of the prior-art inspection systems have been entirely satisfactory. Inspection of reactor vessels and like equipment must be carried out to meet fully the intent of Section XI of the American Society of Mechanical Engineering (ASME) Boiler and Pressure Vessel Code.
In many presently utilized ultransonic inspection systems, a computer controlled remote inspector or instrument carrier (commonly referred to as a "skate") is provided with only enough structure to permit positioning the skate along a track adapted to fit the specific contour of the steam generator, reactor vessel, and the like, to be inspected. The details of one such skate and track, and a method of mounting the track are disclosed in U.S. Pat. No. 3,857,052 assigned to the assignee of this application and incorporated herein by reference.
In order to minimize the size and weight of the remote inspector or skate, only the piezoelectric transducer holding device of the ultrasonic inspection system is mounted on the remote inspector. A transducer is connected to the main control console through a flexible transmission line. The transducer is then periodically pulsed under control of the computer through the transmission line, and echoes sent by the transducer following each pulse are carried back to the main computer console through the same transmission line.
In those systems the transducers are mounted on slider shoes or wheels that are attached to the remote inspector, which moves on the surface of the subject being examined. Vertical, horizontal, and rotational motion of the inspector is provided, and the position is determined by encoders that return this information to the computer.
In accordance with the requirements of the ASME Code, the ultrasonic waves are transmitted at various angles through the subject surface. The current code calls for normal incidence, 45.degree. from normal, and 60.degree. from normal. The 45.degree. and 60.degree. angles are used to detect planar flaws located parallel or transverse to the surface. A 90.degree. or straight-beam is used to detect laminar-type indications and, at high gain settings, planar types.
One such remote inspector or skate presently in use utilizes five transducers installed at various angles. This provides the capability for making a complete inspection (nine view angles) in one pass.
The ASME Code requires inspection, for example, at a number of angles which, if multiple transducers were not used would require multiple passes resulting in longer inspection times. The utilization of a multiple transducer equipped remote inspector necessitates a holding device or remote inspector of increased size and complexity.